At small and medium-sized construction sites it is frequently necessary to mix and transport relatively small amounts of concrete, mortar, gypsum and the like (hereinafter sometimes collectively referred to as "concrete") by mixing the granular base materials, e.g., cement, sand or aggregate with water. The resulting slurry must then be transported to the point of actual use.
In some instances, the mixing operation is done on the ground by forming the granular materials in a pile and pouring water thereover while the materials are manually mixed with a shovel or a similar instrument. This is a slow mixing process requiring a great deal of hand labor and is only economical when the quantity of concrete to be mixed is small. After the mixing, the mixed concrete slurry must be shoveled to the point of use or shoveled into a suitable conveying vehicle, such as a wheelbarrow, for example. For larger applications a separate concrete mixer is sometimes provided which mixes the materials with water to form the slurry. The slurry is then in turn transported to the point of use, frequently by pouring it from the mixer into wheelbarrows.
Although adequate mixing can be accomplished with these prior art methods, the task is relatively tedious. It requires that the concrete slurry be loaded from one container (or from the ground) into a wheelbarrow or the like which increases the labor, the time required for getting the concrete to the point of use and which is, therefore, relatively costly. Even in instances in which a separate concrete mixer is provided the mixer in itself represents a significant investment and is, therefore, costly. Moreover, it clutters up the construction site, it cannot be readily moved about the site to position it closest to the point of use for the concrete. Thus, even separate mixers can be relatively costly to operate.
Attempts have therefore been made to simplify the mixing and transportation of small to modest quantities of concrete as frequently used on small and medium-sized construction sites. U.S. Pat. No. 2,744,735, for example, discloses a combined wheelbarrow-concrete mixer in which the mixer and the drive motor therefor are mounted to the frame of the wheelbarrow beneath a receptacle or container for the concrete and the base materials to be used. Although this device eliminates the multiple transfer of the base materials and/or the mixed slurry from one container to another, the wheelbarrow is heavy and therefore difficult to handle. Moreover, each wheelbarrow is furnished with an entire mixing unit, including the drive therefor which renders it expensive. The cost, coupled with the cumbersome handling of such wheelbarrows significantly detracts from their utility and, as far as is known they have never been commercially accepted.
U.S. Pat. No. 3,820,763 seeks to overcome some of the shortcomings of the above-referenced patent by mounting the concrete mixing unit to a retractable overhead arm which is permanently mounted to a suitable support surface such as the ground. In that patent, the mixing unit depends vertically into the container of a wheelbarrow or the like which is positioned beneath the overhead arm while a rotatable mixing blade is lowered into the container for mixing the concrete. The structure disclosed in this patent eliminates the earlier discussed handling problems of the wheelbarrow due to an excessive deadweight. However, the device is essentially stationary and rather complicated. It requires upright mounting posts which permit vertical travel of the overhead arm to clear the wheelbarrow, multiple joints, linear slide ways, etc., all of which greatly increases the cost of the device.
The following additional U.S. patents disclose a variety of portable mixing apparatus which are considered relevant to the present invention: U.S. Pat. Nos. 1,051,003; 1,161,363; 2,597,688; 3,061,284; 3,185,451; 3,211,436; and 3,450,392.
All of these patents disclose a variety of mixer constructions which have multiple drawbacks so that they have never become accepted to any appreciable extent. Accordingly, there is presently a need for lightweight, inexpensive and portable apparatus which simplifies the concrete mixing operation as well as the delivery of the mixed concrete to its point of use.